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Cutting Metric Theads on a PM1236 lathe

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  • #16
    Originally posted by The Artful Bodger View Post
    He has a PM1236 and there is no need for any approximations.
    I'm sorry, I didn't realise he had a pm1236, thought it was a honda

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    • #17
      I think that one will be wasted on most readers
      .

      Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



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      • #18
        Originally posted by boslab View Post
        I'm sorry, I didn't realise he had a pm1236, thought it was a honda
        I don't understand.

        Harold
        For those having fought for it, Freedom has a flavor the protected will never know.
        Freedom is only one generation away from extinction.

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        • #19
          Don't worry Harold, very subtle English joke
          That's why I said most would not get it
          .

          Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



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          • #20
            No problem. After I gave it some thought, I then surmised that it was an inside joke. I used to work with some English folks in Saudi Arabia and their sense of humor was quite foreign to me. Later, I grew to appreciate their dryness.

            Harold
            For those having fought for it, Freedom has a flavor the protected will never know.
            Freedom is only one generation away from extinction.

            Comment


            • #21
              Originally posted by John Stevenson View Post
              [1] No because you can't use it at all [ see 4 ]

              [2] No screw and half nuts stay the same.

              [3] Problems are without a gear with 127 in it precise metric threads can't be cut but you can get very close approximations. if you are making lead screws you need a 127 gear. If you are making general threads for fastners then there is always a very close approximate.

              [4] Correct that's why [1] is irrelevant.

              If you post a picture of your screw cutting chart and a list of what spare gears came with the machine we can answer in more detail.

              [EDIT] having had a decent amount of experience with these mid sized Chinese lathes they tend not to cut as many corners as the cheaper bench top models and it's rare for them not to have the 127 in the train or supplied as standard.
              Where the main problems occur is when they are second hand the extras tend to disappear. But even that is not a problem as they use usually common across a range of machines so spares are available.
              John,

              There are two large gears seemingly attached to one another. The most outer gear is not in use. The larger of the two (being 127 teeth) is closest to the lathe body. This gear meshes with yjr idler gear.





              I am posting two images of the large gears with the obvious being both images are from different angles.

              Harold
              For those having fought for it, Freedom has a flavor the protected will never know.
              Freedom is only one generation away from extinction.

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              • #22
                There is a bolt behind the big gear which when loosened will allow the big gear to swing up or down on a slotted arm. Loosening the nut in the middle of the big gear allows you to move it along the arm. You use these adjustments to have the centre compound gear engage with different sizes of the other two gears.

                The lower gear has a spacer which can be removed and replaced under that gear and in that way the lower gear can be brought into line with the othermost of the compound gears. Be careful when you take the spacer or small gears off that a small key does not drop on the floor and get lost!

                John

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                • #23
                  Originally posted by The Artful Bodger View Post
                  There is a bolt behind the big gear which when loosened will allow the big gear to swing up or down on a slotted arm. Loosening the nut in the middle of the big gear allows you to move it along the arm. You use these adjustments to have the centre compound gear engage with different sizes of the other two gears.

                  The lower gear has a spacer which can be removed and replaced under that gear and in that way the lower gear can be brought into line with the othermost of the compound gears. Be careful when you take the spacer or small gears off that a small key does not drop on the floor and get lost!

                  John
                  Hi John,

                  In the past, when needing to cut larger threads, I had to switch positions between the 24 tooth gear and the 48 tooth gear. I momentarily lost the key of which you speak. I found it next to the drain. This occurred when I first purchased the lathe. At that time I lived in the lower 48. When building our new home in Alaska, I made certain that no drain was near my lathe. I also am familiar with the need to loosen the center nut on the compound gear (two large gears on the same shaft that are pictured in my recent post). However, I have never been able to figure out how to mesh the 24 & 48 tooth gears with the *never used*"compound gear" until you explained that I place the spacer behind the lower gear. Thanks for that information! However, I don't even know WHY that outer gear is on the lathe because it is never used. In what situation would I use that gear?

                  Harold
                  For those having fought for it, Freedom has a flavor the protected will never know.
                  Freedom is only one generation away from extinction.

                  Comment


                  • #24
                    It seems that your lathe is equipped with the 120/127 gear set, which should let you switch over to metric threading. The chart that Artful showed doesn't show settings for metric thread, otherwise it would show a change from the 120 tooth gear to the 127 tooth gear. It's possible your lathe is equipped for metric, but your chart doesn't show it either. Maybe all you need is the chart-
                    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                    • #25
                      Originally posted by darryl View Post
                      It seems that your lathe is equipped with the 120/127 gear set, which should let you switch over to metric threading. The chart that Artful showed doesn't show settings for metric thread, otherwise it would show a change from the 120 tooth gear to the 127 tooth gear. It's possible your lathe is equipped for metric, but your chart doesn't show it either. Maybe all you need is the chart-
                      Good evening Darryl,

                      I am certain my lathe has the settings for metric. Give me about 15 minutes and I will post an image of my lathe's cover with settings.

                      Harold
                      For those having fought for it, Freedom has a flavor the protected will never know.
                      Freedom is only one generation away from extinction.

                      Comment


                      • #26
                        Originally posted by darryl View Post
                        It seems that your lathe is equipped with the 120/127 gear set, which should let you switch over to metric threading. The chart that Artful showed doesn't show settings for metric thread, otherwise it would show a change from the 120 tooth gear to the 127 tooth gear. It's possible your lathe is equipped for metric, but your chart doesn't show it either. Maybe all you need is the chart-
                        Here it is.


                        Harold
                        For those having fought for it, Freedom has a flavor the protected will never know.
                        Freedom is only one generation away from extinction.

                        Comment


                        • #27
                          OK Harold, picture says it all.
                          Look at the drawing on the LH side, you need to swap the leadscrew gear and spacer over so that the leadscrew gear runs on the 120 tooth gear.

                          Explanation,
                          In your picture you have the 24 driving the 48 with a 127 idler, now the idler makes absolutely no difference the ratio is 24/48 which is 0.5

                          In the picture on the chart the 127 /120 gears are compouned, i.e driven on the same shaft so this calculation comes into the equation and this is that gives ratio that finished up at 25.4 which is the imperial / metric conversion figure.
                          .

                          Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



                          Comment


                          • #28
                            Originally posted by John Stevenson View Post
                            OK Harold, picture says it all.
                            Look at the drawing on the LH side, you need to swap the leadscrew gear and spacer over so that the leadscrew gear runs on the 120 tooth gear.

                            Explanation,
                            In your picture you have the 24 driving the 48 with a 127 idler, now the idler makes absolutely no difference the ratio is 24/48 which is 0.5

                            In the picture on the chart the 127 /120 gears are compouned, i.e driven on the same shaft so this calculation comes into the equation and this is that gives ratio that finished up at 25.4 which is the imperial / metric conversion figure.
                            So you are saying that I CAN do metric with my lathe??

                            If so, I must learn a new way of doing things because, as we've discussed (???) threading is different when doing metric. No chasing dial is used and the half-nut must remain engaged.

                            Harold
                            For those having fought for it, Freedom has a flavor the protected will never know.
                            Freedom is only one generation away from extinction.

                            Comment


                            • #29
                              Yes, so subtle even some of us English folks don't get it.

                              Richard
                              'It may not always be the best policy to do what is best technically, but those responsible for policy can never form a right judgement without knowledge of what is right technically' - 'Dutch' Kindelberger

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                              • #30
                                Harold,
                                Yes you can do metric threads with your lathe.
                                All that is required is you set the gear train and gearbox knobs to what it says on the chart.

                                Once you start threading you cannot disengage the half nuts, you need to go to the end of the thread, stop, retract the tool and reverse the machine back to the start and put another cut on, then repeat.

                                Once you get used to it then it becomes second nature and the dance with the threading dial is omitted

                                In fact I do all my threading, imperial and metric this way and the threading dial has been swinging free for about 12 years.

                                Next stage is to read this thread.

                                http://bbs.homeshopmachinist.net/thr...threading-tool

                                Follow this thru and decide if you can work this way, if you can choose a tool that suits how you work and what you have.
                                Do not take my version as being written in stone, there are many ways to do a job dependant on skills and equipment.

                                However I will say that since doing this tool it has totally transformed threading for me.
                                .

                                Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



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